13 Vegetable Garden Fertilization Tips for Spring

Spring is the perfect time to get outside and work in your garden. From transplanting seedlings to pruning perennials, there are plenty of gardening tasks to keep us busy. Out of all, fertilizing our vegetable garden is usually the top priority. 

Vegetables need plenty of nutrients to fuel them for summer. They use macronutrients such as nitrogen for photosynthesis, potassium for structure, and phosphorus for overall health. They also absorb micronutrients, such as boron, copper, and chloride, for everyday health and vigor. Without an abundance of these nutrients, your vegetables will lack the delicious flavor and texture you expect. 

That’s why fertilizing your vegetable garden in spring is so essential. Your vegetables will get the energy boost they need to grow. However, it’s important to pay attention to several factors when feeding them. Below are the 13 garden fertilizing tips for your spring vegetable garden. 

Test Your Soil

Before you begin, it’s helpful to test your soil to see how productive it is. The best way to do this is to buy a soil testing kit like this one. The kit will tell you which nutrients are in your soil and their concentration. 

With this data, you can tell which nutrients you should amend your soil with. As mentioned above, plants need the macronutrients nitrogen, phosphorus, and potassium. They also need a plethora of micronutrients such as sulfur, boron, copper, calcium, zinc, iron, magnesium, and iodine. 

Your testing kit will tell you other valuable information, such as your soil’s pH, cation exchange capacity, and the percentage of organic material present. These values are important to know because each plant species has its own needs. That’s why some species grow well together in the same soil while others do not. 

Choose the Right Fertilizers

Fertilizers come in a wide range of types. The first thing you should pay attention to is the NPK ratio. This ratio is displayed as three numbers signifying the percentage of nitrogen (N), phosphorus (P), and potassium (K) in the mix. 

For example, a 20-20-20 fertilizer contains 20% nitrogen, 20% phosphorus, and 20% potassium. The remaining 40% is made up of filler content. A fertilizer with a 0-0-22 ratio like this one will have no nitrogen or phosphorus, but will have 22% of its formula composed of potassium. 

You can choose between synthetic, natural, or organic fertilizers. Plant food, such as this all-purpose vegetable fertilizer, is made from all-natural ingredients like alfalfa meal, bone meal, and kelp meal. Other brands contain chemicals and unnatural products. 

I always stick to all-natural or organic plant food for my garden. Decide which type of fertilizer you want to use and buy products you trust. 

Start With Slow-Release Fertilizers

Young plants are extremely sensitive to their new environment. That’s why slow-release granular products perform best in the spring. 

They release even amounts of nutrients over time. They also last a lot longer than liquid plant food. They’re easy to apply, and you can control the amount you’re using. 

During the summer and fall, when you’re vegetables are mature, you can switch to liquid products. They deliver a quicker application of nutrients and are more concentrated. Mature plants can handle the quick burst of energy they provide. 

Understand Your Plants’ Needs

Each plant has its own nutritional needs. Some plants, like tomatoes, are heavy feeders, while others, like rosemary, do better with minimal plant food. Leafy greens love nitrogen-rich plant food, and cucumbers need higher potassium and phosphorus. 

After taking your soil test, you’ll know what your garden bed is lacking. Research each vegetable species you’ll plant and see what type of plant food will benefit them the best. 

Below are a few common spring garden vegetables and their fertilizing needs. This should help you pick the right plant food for your beds.

Peppers

Peppers (Capsicum annum) love plant food with higher amounts of potassium and phosphorus. Ratios of 3-5-5 or 5-10-10 work well. Even better are those with a higher potassium content. Something with an 8:4:32 ratio is what the Food and Agriculture Organization recommends.

Add the plant food to the planting hole when you transplant your seedlings. Apply once again at flowering, then at fruiting, and in the subsequent fruiting stages until the season is out.

Corn

Corn (Zea mays) responds well to a healthy application of a balanced 10-10-10 granular slow-release fertilizer in spring, just before planting. This extra nutrient boost will help the plants put on vigorous growth. 

After the plants start growing, side dress with a light amount of alfalfa meal or feather meal like this one. These plant foods are high in nitrogen, which your corn plants will need for their vertical growth. Repeat two to three more times in the season.

Tomatoes

Tomato plants (Solanum lycopersicum) love plant food with a ratio of 1-3-1. Add slow-release plant food to the planting hole when you transplant your plants. Make sure to evenly distribute the fertilizer and water well so the plant food absorbs into the soil. 

Once your plants are established, you can give them a small amount of liquid fertilizer throughout their growing season. This extra boost in nutrients will help your plants take hold and produce tons of delicious fruits. You can dilute the liquid and feed once per week, or every couple of weeks, for best results.

Lettuce

Lettuce (Lactuca sativa) works well with a light application of alfalfa meal or another slow-release granular fertilizer. Lettuce responds well to plant food with a higher nitrogen content. Lettuce is not a heavy feeding plant, so be careful not to over-fertilize your plants in the spring. 

Peas

Pea plants (Pisum sativum) like a slow-release 10-10-10 or 15-30-15 fertilizer. These plants fix nitrogen in their roots. Add the plant food when you plant your seedlings in the spring. But they need phosphorus to develop pods. Apply once during flowering, and again if there is enough time for a second set of flowers and pods to form for the best results. 

Carrots

Carrots (Daucus carota) are highly sensitive to overfeeding. Only apply fertilizer after doing a soil test. They prefer having higher phosphorus and potassium levels during most of their growing cycle. 

Green Beans

Green Beans (Phaseolus vulgaris) naturally fix nitrogen to the soil via their roots and soil bacteria. Because of this, they’re extra sensitive to plant food that’s high in nitrogen. When you plant your beans, amend the soil with a balanced slow-release product with a ratio of 3-5-5 or similar. 

Radishes

Radishes (Raphanus sativus) love fertilizers high in potassium and phosphorus. Amend the soil just before planting and water it well to evenly distribute the nutrients. You can also use a balanced product as well and reapply once your radishes are mature. 

Onions

Onions (Allium cepa) thrive in soil that’s higher in phosphorus. An organic, slow-release formula works the best. After planting, you can amend the soil with organic compost as the onion plants grow. 

Cabbage

Cabbage plants (Brassica oleracea var. capitata) love a small amount of nitrogen-rich food when they reach the rosette stage in spring. Look for a ratio of around 10-0-0. 

Don’t apply more during the season, as the heads are prone to splitting when too much nitrogen is applied. Instead, add compost or well-rotted manure as a side dressing if it seems like your cabbages need more nutrients.

Kale

Kale (Brassica oleracea var. sabellica) responds well to high amounts of nitrogen throughout its growing season. Nitrogen helps the plant produce tons of chlorophyll for photosynthesis. 

Amend soil beds a few weeks before transplanting seedlings outdoors. If you’re direct sowing your kale seeds, add nitrogen when you thin your seedlings. 

Organic high-nitrogen granular plant food works the best in spring. Add a second side-dressing about four weeks into the season to give your kale an extra boost.  

Pumpkins

Pumpkins (Cucurbita pepo) are heavy feeders. In the beginning stages of growth in spring, these giant plants need a lot of nitrogen. After they form vines, switch to a plant food higher in nitrogen and phosphorus. A 10-3-1 applied once in the season is enough.

Apply slow-release granular fertilizer to your garden beds before planting. I prefer to add compost to the beds as an additional fertilizer. This should give your pumpkins the extra boost they need to grow big, beautiful foliage.  

Amend Annual Beds Before Planting

Vegetables can deplete your soil beds of nutrients, which is why it’s important to fertilize in the spring to replenish the garden for the following year. The best time to do this is right before planting your new crops. 

Young plants will benefit from having the extra nutrients available right away. If you plant your seedlings in nutrient-depleted soil, they’ll have trouble growing. For heavy feeding species like broccoli, tomatoes, or peppers, this could be a big problem. 

Organic or natural granular fertilizers are the best for amending the soil in the spring. They are slow-releasing and gentler on young plants than liquid fertilizers. 

Start by spreading the plant food in your garden bed before planting your vegetables. With clean garden gloves like these, work the plant food into the soil at a depth of around 4 inches. If you have already planted your seedlings, carefully work the plant food around the root system. Be careful not to overly disturb the plant’s roots.

Water Down Concentrated Fertilizers

Unless specified otherwise, many brands should be diluted in water before you apply them. This reduces their strength, making them less caustic to the plant tissue. 

Simply add the fertilizer to a watering can and add it gently to your garden soil. This will help your plants absorb the nutrients slowly without shocking them. 

Always follow the directions on your product to see how much water you should use to dilute it. It’s better to over-dilute your mixture than make it too concentrated. 

Don’t Forget to Water After Applying

After amending the garden beds with fertilizer, don’t forget to water them well. Moisture will absorb the nutrients and distribute them evenly throughout the soil. 

Your vegetables will have an easier time absorbing nutrients once they’ve been absorbed into the soil. Water will carry the nutrients deeper into the soil near the roots of the plants. Over time, the fertilizer will saturate the soil. 

If you skip this step, it could lead to fertilizer buildup at the surface of your garden beds. This could cause serious issues, including fertilizer burns. The nutrients will stay at the surface until you water your beds. This uneven distribution can cause severe issues for your young plants. 

Avoid Feeding Light-Feeders Too Much

Light feeding crops include many herbs, perennials, and native plants. These plants have evolved to survive in poor soil conditions. Too many nutrients could shock the plants and stunt their growth. For herbs, they’ll dramatically impact their flavor. 

When you buy your seeds or starters, research their feeding needs. Avoid overfeeding and amend the soil only if you need to. 

Below are a few common light feeders that prefer less fertile soil. You’ll only have to feed these species when it’s absolutely necessary.

Try Not to Overfeed Your Vegetables

Overfeeding your vegetables is counterproductive. If you use too much plant food, leaves will turn brown or yellow, wilt, or even start to lose their leaves. Before you know it, your crops are ruined. 

If you accidentally add too much plant food in the spring, remove visible buildup on the soil surface. Look carefully for any signs of nutrient or mineral buildup around the base of your plant. 

After removing what’s visible, flush the soil with water without waterlogging it. If the problem is severe, you can transplant your plants into new soil. Be aware of causing transplant shock in vulnerable plants. 

Always follow the application guidelines on your fertilizer’s packet. If you’re unsure, it always helps to wait an extra week to give the plant food extra time to absorb into the soil. 

Mulch Your Beds After Feeding

Mulch is extremely helpful in sealing in nutrients into your soil. It prevents the soil from drying as the summer temperatures rise. It protects the ecosystem underneath your soil by regulating the temperature and keeping predators away. 

After amending your garden beds in the spring, add a thick layer of mulch to the top. Spread it evenly above your beds and water thoroughly. 

If you already have a thick layer of mulch on your garden bed, add your product to the top of the mulch and water well. The water will carry the nutrients into the soil over time. You can also remove a layer of mulch and add the fertilizer around the base of the plants before watering. 

Several types of mulch work well with vegetable gardens. Straw, wood chips, compost, and chopped leaves are my favorites. They are cost-effective, easy to find, and break down easily into the soil over time. 

Don’t Forget Compost

Compost is an excellent source of macro and micronutrients. You can use it liberally to fertilize your spring vegetable garden. If you’re growing heavy-feeding vegetables like tomatoes, corn, and squash, you can amend your beds with compost throughout the growing season. 

The best time to start is in spring, just before and after planting your young plants. The extra organic material and nutrients will break down slowly over time. 

Compost is easy to make at home and only takes a simple setup. Balance the amount of brown and green waste. The more earthworms and beneficial insects in your compost pile, the better. 

I prefer to amend my garden beds with compost first, before fertilizing. This helps promote microbial growth below the root system. 

Avoid Adding Too Much Nitrogen

Too much nitrogen can be harmful to plants such as tomatoes, beans, and peppers. Nitrogen can be helpful in small amounts, but too much can cause leggy growth. It can also affect flower and fruit production. Nitrogen runoff is a huge environmental problem, too, that leads to eutrophication of sensitive waterways.

If you’re unsure, test your soil before planting. Make sure to group nitrogen-loving plants together. Plant vegetables that are more sensitive to nitrogen together. 

Nitrogen can greatly diminish the aromatic compounds in popular herbs like rosemary and basil. Always apply less than you think you’ll need just to be safe. 

Feed Your Container-Grown Veggies More

Nutrients leach from the soil faster in containers. There is less surface area to absorb nutrients. Watering your plants and day-to-day nutrient absorption will deplete nutrients over time. 

If you’re growing container vegetables, amend the soil more frequently in spring. Keep applying plant food throughout the growing season, especially for heavy-feeding varieties like tomatoes, squash, and artichokes.  

Because of the smaller spaces, it’s also easier to overfeed your container plants. Always follow your product’s directions to avoid overfeeding. If your plant is showing signs of too much fertilizer, stop feeding immediately.